1. Field of the Invention
This invention relates to improvements in manufacturing and operating techniques for mass data storage devices, and the like, and more particularly to improvements in methods and apparatuses for characterizing asymmetries of an MR read head, or the like, for use therein.
2. Relevant Background
Mass data storage devices include tape drives, as well as hard disk drives that have one or more spinning magnetic disks or platters onto which data is recorded for storage and subsequent retrieval. Hard disk drives may be used in many applications, including personal computers, set top boxes, video and television applications, audio applications, or some mix thereof. Many applications are still being developed. Applications for hard disk drives are increasing in number, and are expected to further increase in the future.
One class of mass data storage devices to which the present invention has particular applicability is hard disk drive systems. A hard disk drive system typically includes a rotating magnetic disk on which information is recorded. A read transducer is movably supported adjacent the magnetic disk for reading the prerecorded information from the disk. The read transducer typically flies above the surface of the disk, being supported by an xe2x80x9cair bearingxe2x80x9d that is created by the spinning disk, so that the transducer does not touch the surface of the disk in normal operation.
Recently, magnetoresistive (MR) heads have been gaining wide popularity for use as the read transducer. The term xe2x80x9cmagnetoresistancexe2x80x9d refers to the change in resistivity of the materials of the head in the presence of a magnetic field. The introduction of MR heads into disk drives has significantly increased the areal density. However, due to the characteristics of the head materials, changes in resistance in response to equal positive and negative magnetic fields are not necessarily symmetrical. This is referred to as head xe2x80x9casymmetryxe2x80x9d.
Typically, a circuit is included in the read channel of the mass data storage device in which the MR head is employed to compensate for such asymmetrical signal responses. However, the asymmetrical responses are in large part nonlinear, and are difficult to assess and compensate.
What is needed, therefore, is a method for more accurately characterizing asymmetries of an MR head in a mass data storage device, or the like.
In light of the above, therefore, it is an object of the invention to provide a method for characterizing asymmetries of an MR head in a mass data storage device, or the like.
This and other objects, features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the invention, when read in conjunction with the accompanying drawings and appended claims.
According to a broad aspect of the invention, a method is disclosed for characterizing asymmetries of a magneto-resistive type head in proximity to a magnetic media, such as a magnetic disk of a hard disk drive, or the like. The method includes using the magneto-resistive type head to read a continuous signal from the magnetic media to provide a read back signal. Energies contained in the read back signal which occur in excess of a predetermined threshold for the positive and negative portions of the read back signal are then determined. The energies may be determined by accumulating sampled signal values from the read back signal during times at which the read back signal exceeds the threshold.
According to another broad aspect of the invention, a method is disclosed for characterizing asymmetries of a magneto-resistive type head in proximity to a magnetic media. The method includes writing a continuous signal onto the magnetic media, and using the magneto-resistive type head, reading back the continuous signal to provide a read back signal. The positive and negative portions of the read back signal are then compared to a threshold value, and energies contained in the read back signal occurring in excess of the threshold value for the positive and negative portions of the read back signal are determined, for example by accumulating sampled signal values from the read back signal during times at which the read back signal exceeds the threshold.
According to another broad aspect of the invention, an apparatus for determining asymmetries of a magneto-resistive type head in proximity to a magnetic media is disclosed. The apparatus includes a comparator for determining when positive and negative signals produced by the head in reading a continuous signal from the disk exceed known thresholds, and an energy determining circuit for measuring energies contained in the positive and negative read back signals when the read back signals exceed the thresholds. The energy determining circuit may include a circuit for sampling the read back signals at least during times at which the read back signal exceeds the threshold to produce sampled signal values therefrom, and an accumulator for accumulating the sampled signal values.